Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
In general, a cellular wireless network may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to UEs defining a downlink or forward link and communications from the UEs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WIMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of UEs, initiation of communications, handoff between coverage areas, and functions related to air interface communication.
In accordance with the air interface protocol, each coverage area may operate on one or more carrier frequencies or range of carrier frequencies In a frequency division duplex (FDD) arrangement, different carrier frequencies or ranges are used for the downlink than the uplink. Whereas, in a time division duplex (TDD) arrangement, the same carrier frequency or range is used for the downlink and uplink and is allocated over time among downlink and uplink communications.
Further, each coverage area may also define a number of air interface channels for carrying information between the base station and the UEs. These channels may be defined in various ways, such as through frequency division multiplexing, time division multiplexing, and/or code-division multiplexing, for instance. By way of example, each coverage area may define a pilot channel, reference channel or other resource on which the base station may broadcast a pilot signal, reference signal, or the like that UEs may detect as an indication of coverage and may measure to evaluate coverage strength. As another example, each coverage area may define an uplink control channel or other resource on which UEs may transmit control messages such as registration requests and access requests to the base station. And each coverage area may define a downlink control channel or other resource on which the base station may transmit control messages such as system information messages and page messages to UEs. Each coverage area may then further define one or more uplink and downlink shared channels, such as traffic channels or other resources, which the base station may allocate for use on an as-needed basis to carry communications between the base station and served UEs.
When a UE first powers on or enters into a base station's coverage area, the UE may “attach” with the base station, by transmitting an attach request to the base station. The attach request may cause the base station or associated infrastructure to authenticate and authorize the UE to be served by the base station and to reserve network resources for use to serve the UE. For instance, the attach request may result in setup of one or more virtual bearer connections extending in the network between the base station and one or more transport networks and extending over the air interface as a radio link between the base station and the UE.
Once the UE is attached with a base station, the UE may operate in a connected mode or an idle mode. In the connected mode, the UE may engage in communication of bearer data (e.g., application layer communications, such as voice communication, video communication, file transfer, gaming communication, or the like), transmitting bearer data on uplink traffic channel resources to the base station and receiving bearer on downlink traffic channel resources from the base station. After a timeout period of no bearer data communication, or for other reasons, the UE may then transition from the connected mode to the idle mode, with the base station releasing the radio link portion of any bearer connections assigned to the UE so as to conserve air interface resources. In the idle mode, the UE may then simply monitor a downlink control channel to receive overhead information and to check for any page messages. And the UE may engage in signaling with the base station to transition back to the connected mode if and when the UE receives a page message from the base station indicating an inbound bearer communication or if and when the UE seeks to engage in outbound bearer communication.